The goal of this project is to study the effects of various bone-active hormones on specific bone cell types. Matrix free bone cells obtained by sequential enzymatic digestion of mouse calvaria have been shown to be enriched in biochemical activities regarded as characteristic of either osteoclasts or osteoblasts. These cells provide a relatively simple experimental system for studying differential hormone effects on bone formation and/or resorption as indicated by the activities of these cells. Using these cells, we have shown that gluocorticoids modulate basal osteoclastic activities at physiological concentrations, and inhibit osteoblasts at pharmacological concentrations, and also increase the sensitivity of bone cells to hormones that stimulate bone resorption. The specificity of these hormonal interactions, and the ionic requirements, are now being investigated.